The reduction in size of semiconductor components and increased usage of semiconductor processors has lead to an explosion of new electronic devices. Most, if not all, of these electronic devices require some amount of memory in order to function. The proliferation of such devices has significantly increased demand for memory that is efficient in size as well as power consumption. Smaller sized semiconductor components and memories have made numerous hand held electronic devices feasible. Examples of hand-held devices include cell phones, personal radios, walkie-talkies, personal data assistants, palm pilots, pagers, notebook computers, remote controls, voice recorders, audio recorders, video recorders, radios, small televisions, web viewers, cameras, and the like. Although some electronic devices require only relatively small amounts of memory, many newer electronic devices require an increasing amount of memory. For example, digital cameras, digital audio players, personal digital assistants, and the like generally seek to employ large capacity memory components, such as, for example, flash memory cards, smart media cards, compact flash cards, pen drives and/or other similar devices.
Memory components are typically divided into volatile memory and non-volatile memory. Volatile memory components generally do not retain information stored or programmed within them when power is removed from the component. Such memories typically require periodic refresh cycles to maintain their information. Volatile memory components include most forms of random access memory (RAM). RAM is available in many forms such as, for example synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM). In contrast, non-volatile memory components retain their information even when power is removed. Examples of non-volatile memory components include; ROM, programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash EEPROM, and the like. Comparatively, volatile memory components generally provide faster operation at lower cost than non-volatile memory components.
In many instances, such memory components comprise at least one array of memory elements and associated semiconductor control elements to support various functions like the ability of being repeatedly “written”, “erased”, and/or “read”. A memory element with supporting semiconductor elements can be referred to as a memory device, and a memory component comprises a plurality of such memory devices. Individual memory elements in a memory component can be “written” with information, can be “erased”, or can be “read”. Individual memory elements are generally programmed or written to an “on” state (e.g., a logic “1”) or erased to an “off” state (e.g., a logic “0”). When a memory component is “read”, the information (e.g. the “on” state or “off” state) is retrieved in such a manner that the state of the individual memory elements remains unaltered. Typically, a memory component is addressed in order to be written, erased, or read. Control lines generally referred to a wordlines and bitlines or row address select (RAS) and column address select (CAS) lines control access to specific memory devices for purposes of writing, erasing or reading a specific memory element. Memory components are often fabricated with inorganic solid state technology, such as, crystalline silicon devices. A common semiconductor device employed in memory elements is the metal oxide semiconductor field effect transistor (MOSFET).
Memory component developers and manufacturers are constantly striving to increase storage capacity and to reduce cost of manufacture for memory components. To increase device densities, manufacturers typically focus on scaling down semiconductor device dimensions (e.g. at sub-micron levels). In order to accomplish such densities, smaller feature sizes and more precise feature shapes are often required. This may include the width and spacing of interconnecting lines, spacing and diameter of contact holes, and the surface geometry, such as corners and edges, of various features. A postage-stamp-sized piece of silicon may contain tens of millions of transistors, each transistor as small as a few hundred nanometers. A resulting memory component will often comprise a multitude of individual semiconductor layers requiring numerous fabrication steps to complete. In general, more complex devices require more individual layers to implement. With the size of semiconductor features decreasing and number of layers increasing, sensitivity to alignment tolerances makes fabrication markedly more difficult. As the number of layers required to produce a semiconductor device increases, manufacturing defects generally increase and, therefore, the yield decreases.